The MSM-04 ACGGUY is an aquatic combat/general use mobile suit. Equipped with two 6-tube rocket/torpedo launchers and a small mobility assistance pack, the ACGUY is comparatively lightly armed; however, it is a deadly opponent in the right circumstances, able to unleash an explosive hell on an unsuspecting enemy. Some field reports even note that the launchers can be effectively used as bludgeons.

Chiefly designed for the Marine branches of service, the ACGUY was deemed "too cutesy" and therefore rarely employed in traditional roles. Special Forces units quickly latched onto the widely unloved mobile suit, seeing the value in the ACGUY's underwater capabilities for their sneak attack potential. Often utilized as scouts or raiders, the ungainly suits have a feared reputation among enemy ranks.

Many ACGUY pilots deck their mobile suit out in custom paint jobs depending on mission specifics, resulting in a wide array of coloration and camo schemes. An Arctic camo scheme is pictured.